package chapter5;

import java.util.Date;

import org.bouncycastle.asn1.*;

/**
 * Implementation of an example ASN.1 structure.
 * <pre>
 * MyStructure ::= SEQUENCE {
 *                   version INTEGER DEFAULT 0,
 *                   created GeneralizedTime,
 *                   baseData OCTET STRING,
 *                   extraData [0] UTF8String OPTIONAL,
 *                   commentData [1] UTF8String OPTIONAL }
 * <pre>
 */
public class MyStructure implements ASN1Encodable {
    private ASN1Integer version;
    private DERGeneralizedTime created;
    private ASN1OctetString baseData;
    private DERUTF8String extraData = null;
    private DERUTF8String commentData = null;

    /**
     * Constructor from an ASN.1 SEQUENCE
     */
    public MyStructure(ASN1Sequence seq) {
        int index = 0;

        // check for version field
        if (seq.getObjectAt(0) instanceof ASN1Integer) {
            this.version = (ASN1Integer) seq.getObjectAt(0);
            index++;
        } else {
            this.version = new ASN1Integer(0);
        }

        this.created = (DERGeneralizedTime) seq.getObjectAt(index++);
        this.baseData = (ASN1OctetString) seq.getObjectAt(index++);

        // check for optional fields
        for (int i = index; i != seq.size(); i++) {
            ASN1TaggedObject t = (ASN1TaggedObject) seq.getObjectAt(i);

            switch (t.getTagNo()) {
                case 0:
                    extraData = DERUTF8String.getInstance(t, false);
                    break;
                case 1:
                    commentData = DERUTF8String.getInstance(t, false);
                    break;
                default:
                    throw new IllegalArgumentException("Unknown tag " + t.getTagNo() + " in constructor");
            }
        }
    }

    /**
     * Constructor from corresponding Java objects and primitives.
     */
    public MyStructure(
            int version,
            Date created,
            byte[] baseData,
            String extraData,
            String commentData) {
        this.version = new ASN1Integer(version);
        this.created = new DERGeneralizedTime(created);
        this.baseData = new DEROctetString(baseData);

        if (extraData != null) {
            this.extraData = new DERUTF8String(extraData);
        }

        if (commentData != null) {
            this.commentData = new DERUTF8String(commentData);
        }
    }

    /*
     * Produce an object suitable for writing to an ASN1/DEROutputStream
     */
    public DERSequence toASN1Object() {
        ASN1EncodableVector v = new ASN1EncodableVector();

        if (version.getValue().intValue() != 0) {
            v.add(version);
        }

        v.add(created);
        v.add(baseData);

        if (extraData != null) {
            v.add(new DERTaggedObject(false, 0, extraData));
        }

        if (commentData != null) {
            v.add(new DERTaggedObject(false, 1, commentData));
        }

        return new DERSequence(v);
    }

    @Override
    public ASN1Primitive toASN1Primitive() {
        return this.toASN1Object();
    }
}
